A light modulator which performs light modulation by changing the reflection direction of incident light on an optical switch device using an electrostatic force, is employed in an light information processing apparatus which processes light information, an image formation apparatus which writes optical data by an electrophotographic process and forms an image, an image projection and display apparatus which projects and displays an image, or the like.
As for the light modulator which performs light modulation by changing the reflection direction of incident light on an optical switch device using an electrostatic force, a device which bends a cantilever by an electrostatic force and changes and switches the reflection direction of the incident light and a light modulation system using the switch device are well known. The cantilever oscillates when the electrostatic force is released and the bending of the cantilever is recovered. This is because the free oscillation of the cantilever is generated by fixing only one end of the cantilever.
In addition, if the cantilever is formed out of a thin film, a residual stress is generated. The cantilever is deformed by the residual stress. Further, since the residual stress is reduced with the passage of time, the deformation state of the cantilever changes with the passage of time. For these reasons, the cantilever has low stability.
Furthermore, in case of the cantilever, signal response is deteriorated due to the free oscillation thereof.
Therefore, it is disadvantageously difficult to ensure the stability of the cantilever and the natural frequency of the cantilever is low, with the result that the response speed cannot be disadvantageously accelerated.
A device which holds a mirror by a thin torsion bar, changes the direction of the mirror by an electrostatic force and changes the reflection direction of light to thereby switch light is also well known. However, since the structure of the device is too complicated, it is difficult to improve yield. In addition, since the mirror is held by the thin torsion bar, the service life of the device cannot be lengthened.
Further, a device which drives a diffraction grating by an electrostatic force and switches light is well known (see Japanese Patent Nos. 2941952 and 3016871 and Japanese Patent Application National Publication (Laid-Open) No. 10-510374 and the like).
However, the device which drives a diffraction grating by an electrostatic force and switches light, has a disadvantage in that the wavelength of incident light to be used is limited.
Furthermore, a device which bends a beam by an electrostatic force, adjusts the focus of reflection light and passes the reflection light through a slit to thereby switch light is well known (see Japanese Patent Application Laid-Open No. 2000-2842).
However, with the device which bends a beam by an electrostatic force, adjusts the focus of reflection light and passes the reflection light through a slit to thereby switch light, the bending degree of the beam becomes often unstable, disadvantageously deteriorating the reliability of the device.
As explained above, the conventional light modulators each of which modulates light by changing the reflection direction of an incident light beam, a light information processing apparatus which includes the conventional light modulator, an image formation apparatus which includes the conventional light modulator and an image projection and display apparatus which includes the conventional light modulator have disadvantages in that the structure of changing the reflection direction of an incident light beam and thereby modulating light is complex, response is slow, the wavelength of the incident light to be used is limited, operation is unstable and reliability deteriorates.